Stabilization of Transition-Metal Complexes in High Oxidation States by Macrocyclic Tertiary Amines. Electrochemical Generation and Spectroscopic Properties of Novel Dihalogeno and Pseudohalogeno Tetraamine Complexes of Ruthenium(IV)

Chi Ming Che, Kwok Yin Wong, Chung Kwong Poon

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Abstract

1,4,8,12-Tetramethyl-1,4,8,12-tetraazacyclopentadecane (15-TMC) was synthesized by the reaction of 1,4,8,12-tetraazacyclo-pentadecane with formaldehyde. Reactions of K2[RuCl5H2O] with 15-TMC and 16-TMC (16-TMC = 1,5,9,13-tetramethyl-1,5,9,13-tetraazacyclohexadecane) in ethanol yielded trans-[RuLCl2]Cl (L = 15-TMC and 16-TMC, respectively) in high yields. The syntheses of trans-[RuLBr2]ClO4[L = (TMEA)2(TMEA = N,N,N',N'-tetramethyl-1,2-ethanediamine), 14-TMC (1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane), and 15-TMC], trans-[Ru(TMEA)2(NCS)2]NCS, and trans-[Ru(14-TMC)(CH3CN)2] [ClO4]2are also described. The electrochemistry of trans-[RuLX2]+[L = (TMEA)2, 14-TMC, 15-TMC, and 16-TMC; X = Cl, Br, and NCO] in acetonitrile were examined. The Ef° values of trans-[RuLCl2]Cl in 2 M HCl have been found to decrease with L in the order 14-TMC > 15-TMC > 16-TMC. Reversible/quasi-reversible Ru(IV)/Ru(III) couples in acetonitrile with Ef° values ranging from 1.05 to 1.27 V vs. the ferrocene couple were observed. Controlled-potential electrolyses of trans-[RuLX2]+at 1.30 V vs. the ferrocene couple generated some novel trans-[RuIVLX2]2+complexes. The ligand-to-metal charge-transfer transitions in the UV-vis spectra of trans-[RuIV(TMEA)2X2]2+have been identified at 410 (X = Cl) and 570 nm (X = Br), which are considerably red-shifted with respect to their Ru(III) counterparts.
Original languageEnglish
Pages (from-to)1809-1813
Number of pages5
JournalInorganic Chemistry
Volume25
Issue number11
DOIs
Publication statusPublished - 1 Jan 1986
Externally publishedYes

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry

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